Van Leisure switching AGM to LiFePo4

[macasas]

Sorry if posted in the wrong list.

I have a small day van. Non-smart alternator 13.8-14.6V when running. 120W single solar panel on the roof. I use a Ring RSCDC30 charger which allows vehicle battery and solar connection, auto switches to solar when engine is off and auto switches to engine when running. All of this is charging 2 x 110Ah AGM batteries connected to lights, a fridge, USB and DC outlets for charging laptops and phones.

Recently noticed fridge is turning off at night due to low voltage, and can no longer charge laptop late in the day as batteries do not have time to recharge. So things are going south!

Bought 2 x 100Ah LiFePo4 batteries as a replacement or addition, but realise I need to change the Ring Charger as well, as its not suitable to LiFePo.

Q1. I've seen B2B system like CTEK D250SE and the 30A Dual-Input DC-to-DC MPPT and these might be the best choice, but I keep reading about separates, to gain more control of user settings, to only replace individual items if something breaks. Can anyone give me some examples of what I'd need in a separates type of system? The auto switching to vehicle when running is probably the only thing.

Q2. Is there anything else I need to be aware of when switching over, it would be good not to start having fires and stuff.

Thanks very much for any help.

 

[mikefitz]

what I'd need in a separates type of system?

For alternator charging a Victron DC to DC charger, 30 or 50 amp rating. These auto detect engine charging
For solar charging a Victron Smart Solar controller , 10 or 15 amp rating.
You can Interface to Victron units vai a Bluetooth app, Victron connect.

need to be aware of when switching

A 'master ' fuse on each battery positive, MRBF type with Bluesea fuse holder . Rated for the cables you have connected to the battery, for example if you have 16mm2 cable, maximum allowed current 110 amps, from the battery to the acessories fuse box, you need a 50A fuse on each battery before the parallel conection.

You can get the chargers from Amazon or any Victron distributer. I will give links as examples using the 12v planet store.
DC to DC charger,
30A charger
50A charger
solar controller, with a 120 panel you need a 10A or 15A controller,
15A solar controller
MRBF fuse,
50A fuse
fuse holder, bolt to battery positive terminal,
Holder

You need a fuse box with blade fuses for the acessories, 6 or 12 way
Fuse box
The cable to the solar controller, suggest 4mm2 or 6mm2, connect to the battery via a 15A blade fuse in the fuse box.

The cable from the starter battery to the DC to DC charger and to the leasure battery , together with fuses at each battery will depend on the units power. Examples for the 30A unit,
Cable 10mm2, fuse at starter battery and leisure batteries parallel point, 60A.
60A fuse
fuse holder,
Holder

 

[macasas]

Thanks for the comprehensive answer, just one question (hopefully not a stupid one).. if I connect a 30A charger to my alternator and leisure battery, and then add a solar controller to my leisure battery, who is in control of where the charge comes from (alternator or solar) or do they just mix together and go into the leisure batteries without a problem of backfeeding each controller?